Self-tackifying xerographic toner



March 5, 1963 c. J. CLAUS 3,080,250

SELF-TACKIFYING XEROGRAPHIC TONER Filed March 13, 1958 INVENTOR.

Carl J. Claus ATTORNEY wherein an electrostatic United States 3,080,250 SELF-.TACKlFYING XERGGRAIHEC TGNER Carl J. Claus, Rochester, N.Y., .assignor' to Xerox Corporation, a corporation of New York Filed Mar. 13, 1958, Ser. No. 721,1%9

4 Claims. (Cl. 11717.5)

This invention relates in general to electrostatic recording and in particular to materials and methods for xerography. I

In the art of xerography, it is usual to-form an electrostatic image on a suitable insulating or photoconductive insulating surface and to develop this image, or in other 'jwordsmake it'visible, by presenting to the surface an electroscopic marking material. of xerography the electrostatic image is formed on a photoconducti ve insulating surface by charging the sur- In the usual embodiments face and exposing it to an image of light and shadow to "be recorded whereupon the electric charge is dissipated in the light areas. conventionally the image is then developed by dusting the image bearing surface with highly colored pigment materials such, as for example, pigmented thermoplastic resins. Because of requirements of transfer of the powder and re-use of the photoconducting surface, and for other reasons, xerographic development has been usually limitedto dry powder materials. In these prior-procedures, therefore, it has generally been necessary to employ subsequent fixing steps or operations in order to cause the image material to adhere permanently either to the original image bearing surface or to such other surface as shall be "desired for a final image support member. Existing fixing operations have generally been limited to'fusing the image material by means I of heat or solvent vapor, although other methods such as lacquer spraying, overlaying and the like have occasionof the invention is to provide a new electroscopic image developing material for xerographic recording which image material is capable of being deposited in response to an electrostatic charge pattern and subsequently fixed on an image support surface by means of pressure.

An additional object of the invention is to provide a new xerographic developing material comprising an encapsulated material including a liquid droplet of an adhesive composition within a shell having surface triboelectrio properties for electrostatic deposition.

Additional objects of the invention will in part be obvious and will in part become apparent from the following specification and drawing in which:

The FIGURE is a diagrammatic view of a developer powder particle according to one form of the invention.

It has recently been found that suitable liquid materials can 'be formed into an extremely finely divided dry composition by separate encapsulation of appropriate liquid droplets within a hydrophilic shell. For example, in US. Patent 2,800,458, there is disclosed a manufactured preparation of oil-containing capsules of hardened gelatin. Now, in accordance with the present invention, encapsulated materials mayb formulated with adhesive or tackifying agents within an outer shell suited for xerographic development and electrostatic recording. It has now been found that image forming powders of proper triboelectric properties can be produced by encapsulating a liquid droplet of a suitable adhesive or tackifying material within a hydrophilic coating such as gelatin or the like, and in turn encapsulating the hydrophilic material within a tough hydrophobic resin coating. Furthermore, outer coatings VCIllI.

. 3&39259 Patented Mar. 5, 1963 2 of the polystyrene family including polymerized styrene, polystyrene homologues and mixtures and copolymers thereof, and resins of the acrylic esters acrylic amide and methacrylic esters and amides and mixtures of copolymers thereof, as well as mixtures of styrene and acrylic resins may be produced on hydrophilic capsules by immersion in polymer solutions followed by drying or evaporation of the solvent to produce developer materials for xerography, while liquids included within the capsule may be incompatible with such resins.

The new developer powder composition includes essentially three separate phases or components such as, for example, a liquid droplet 1i) encased in a hydrophilic coating 11, in turn within ahydrophobic resin co-atinglZ.

The liquid composition may include an oil base dye, ink, or the like, containing a highly colored material such as a pigment or dye generally capable of permanently coloring an image support sheet such as, for example, a sheet of paper or the like. Suitable oil bases include oils and other fluids generally not miscible with water but such suitable solvents and tackifying materials are generally characterized by being inert with respect to theihydrophilic capsule wall and by dissolving or partially dissolving, or otherwise softening the outer hydrophobic resin: For example, desired solvents and tackifiersfor use in conjunction with polystyrene-type and acrylic type hydrophobic resins include: trichloroethylene,benzene, toluene, xylene, and Krylon or a resin dissolved ina drying sol- The essential component of this droplet is the tackifier or material capable of softening or dissolving the resin coating and rendering the resin sticky.. The term tackifier as used in the specification and claims therefore, denotes such a material miscible or soluble withthe coating resin and operable when mixed therewith to make --mixture of styrene and styrene homologues and available under the name Piccolastic D-l25 is employed. This resin is d ssolved in xylene, and the capsules are immersed in the solution. Excess liquidis filtered on and the coated capsules air dried with occasional mixing. A1- ternatively the capsules may be dried according to conventional spray drying procedures.

In the preferred procedure for producing a xerographic developer the capsule powder is mixed with a granular bead-like carrier material such as disclosed in Walkup Patent US. 2,816,551, generally in the amount of 1% of the powder composition and 99% of the carrier composition. The mixed developer material is useful in xerographic image development as, for example, by cascading the mixture across the surface of the electrostatic image bearing xerographic plate or across the surface of an electrostatic image bearing insulating surface.

Alternatively, the powder material may be employed for image development by blowing it into an air cloud and directing the air cloud to the image surface, by mixing the powder material with a ferromagnetic material and magnetically conveying the mixture into brushing contact with the image surface, or by dusting the powder material into a brush such as, for example, a fur brush and brushing the image surface. Other image development methods may include dispersing the powder in an inert nonpolar liquid and applying a liquid suspension by dipping or immersing or by pouring the liquid suspension across the image surface or the like.

Upon image development in any of these methods it has been found that a visible powder image is formed on the image bearing surface. The image may be permanently alfixed to the surface by means of pressure rollers or the like, or may be transferred to an adjacent surface and subsequently aflixed to such an adjacent surface. Thus, for example, a Xerographic image may be formed on a selenium coated metal plate or drum by applying an electrostatic charge to the selenium surface. The image may be developed by the methods of the invention and transferred to a piece of paper placed in contact with the image bearing selenium plate or drum by means of corona discharge or the like and the image permanently affixed to the paper by means of pressure rollers. Likewise, an electric image formed on a paper backed photoconductor such as zinc oxide in an insulating silicone, polystyrene, acrylic resin or the like, may be developed and fixed in situ. Upon crushing the capsule, as by means of pressure rollers or the like, the liquid adhesive or tackifier mixes with the hydrophobic resin coating to form a permanently fused image.

The present invention permits the use of Xerography of a wide variety of color marking materials including dyes, inks, or the like, without regard to the triboelectric properties of such marking materials. There may be employed, for example, carbon black materials prepared and coated according to this invention to have suitable triboelectric properties as well as dyes, pigments, or the like, of various colors dispersed or dissolved in oil base. In addition, it provides a self-contained image fixing material. The xerographic developer compositions prepared with such marking materials are independent of the triboeleotric characteristics of the marking material itself or of the encapsulating materials in which the marking materials are encased. It has been found that desire-d triboelectricity and humidity resistance can be imparted to the composition by polymerized styrene and polymerized acrylic resins and that such resins may be employed Without regard to the nature of the marking material or to oil base.

By mean-s of the present invention, simplification of apparatus and methods can be achieved and fixing of the developed image can be accomplished in a straightforward, simple manner. In addition, small amounts of solvent or tackifier can be employed so as to avoid both solvent recovery and toxicity problems generally associated with solvent fixing.

What is claimed is:

1. A self adherent xerographic toner composition consisting of particles triboelectrically adapted independently of ambient humidity and in a size range for use in conjunction With a Xerographic carrier to form a toner car- T161 system for developing xerographic images, said paticles consisting of an outer shell of hydrophobic resin triboelectrically adapted for use with a xerographic carrier and coated upon an intermediate rupturable shell of hardened colloid, and an inner core of solvent for said outer shell, said colloid normally separating said resin from said solvent core.

2. The composition of claim 1 in which said inner core contains a marking material.

3. The composition of claim 1 in which said outer shell of hydrophobic resin comprises a resin selected from the group consisting of polystyrene and polyacrylic resins.

4. The method of xerography comprising forming an electrostatic image corresponding to information to 'be recorded, forming a pattern of xerographic toner on an image receiving surface by means of said electrostatic image, said toner consisting of particles triboelectrically adapted independently of ambient humidity and in a size range for use in conjunction with a xerographic carrier to form a toner carrier system for developing xerographic images, said particles consisting of an outer shell of hydrophobic resin triboelectrically adapted for use with a xerographic carrier and coated upon an intermediate rupturable shell of hardened colloid and an inner core of solvent for said outer shell, said colloid normally separating said resin from said solvent core, and rupturing said colloid shells whereby the hydrophobic resin shells are tackified by said solvent and adhered to the image receiving surface.

References Qited in the file of this patent UNITED STATES PATENTS 1,805,308 Dixon May 12, 1931 2,512,192 Yen et al June 2-0, 1950 2,712,507 Green July 5, 1955 2,730,456 Green et al. Jan. 10, 1956 2,784,109 Walkup Mar. 5, 1957 2,788,288 Rheinfrank et al Apr. 9, 1957 2,800,458 Green July 23, 1957 2,891,911 Mayer June 23, 1959 2,953,470 Green et a1 Sept. 20, 1960 FOREIGN PATENTS 20,726 Great Britain of 1910 1,112,180 France Nov. 9, 1955 760,403 Great Britain Oct. 31, 1956 

4. THE METHOD OF XEROGRAPHY COMPRISING FORMING AN ELECTROSTATIC IMAGE CORRESPONDING TO INFORMATION TO BE RECORDED, FORMING A PATTERN OF XEROGRAPHIC TONER ON AN IMAGE RECEIVING SURFACE BY MEANS OF SAID ELECTROSTATIC IMAGE, SAID TONER CONSISTING OF PARTICLES TRIBOELECTRICALLY ADAPTED INDEPENDENTLY OF AMBIENT HUMIDITY AND IN A SIZE RANGE FOR USE IN CONJUNCTION WITH A XEROGRAPHIC CARRIER TO FORM A TONER CARRIER SYSTEM FOR DEVELOPING XEROGRAPHIC IMAGES SAID PARTICLES CONSISTING OF AN OUTER SHELL OF HYDROPHOBIC RESIN TRIBOELECTRICALLY ADAPTED FOR USE WITH A XEROGRAPHIC CARRIER AND COATED UPON AN INTERMEDIATE RUPTURABLE SHELL OF HARDENED COLLOID AND AN INNER CORE OF SOLVENT FOR SAID OUTER SHELL, SAID COLLOID NORMALLY SEPARATING SAID RESIN FROM SAID SOLVENT CORE, AND RUPTURING SAID COLLOID SHELLS WHEREBY THE HYDROPHOBIC RESIN SHELLS ARE TACKIFIED BY SAID SOLVENT AND ADHERED TO THE IMAGE RECEIVING SURFACE. 